Electric Power Steering (EPS) systems use an electric motor, a coupling mechanism, and an electronic control module to assist a driver when steering a vehicle. One of the primary objectives of such a system is to be able to provide high levels of assist for steering a vehicle with high steering loads. During this condition the EPS system provides higher gain/assist values as higher driver torque levels are sensed. To maintain system stability during this operating condition a compensation scheme is used.
While the compensation filter enhances system stability, it can also degrade steering feel, particularly during on-center driving. In an effort to improve on-center steering feel, tuning engineers can use a vehicle velocity dependent compensator blend (VDCB) function to decrease the effect of the compensator filter at higher vehicle speeds.
However, the above approach does not differentiate between the levels of steering assist gain. This limitation often requires tuning engineers to compromise between on-center steering feel and system stability. If not tuned optimally, the approach may drive the system to be unstable at certain operating conditions.